The present invention relates to a positioning device suitable for use in positioning various precision processing devices and precision measurement devices, to an exposure device using said positioning device, for use in a lithography step in semiconductor manufacturing, and to a method of manufacturing said device.
Devices conventionally used as exposure devices in manufacturing semiconductor elements include a device called a stepper and a device called a scanner. In a stepper, a semiconductor wafer on a stage device is moved by steps under a projecting lens, while a pattern image formed on a reticle is reduced and projected onto the wafer by the projecting lens so as to successively expose a plurality of positions on a single wafer. In a scanner, a semiconductor wafer on a wafer stage and a reticle on a reticle stage are moved relative to a projecting lens, and, by illumination by a slit-shaped exposure light during the scanning motion, the reticle pattern is projected onto the wafer. The stepper and scanner are, from the point of view of performance (resolution, precision of superimposition, etc.), the most favored exposure devices.
With regard to the semiconductor wafers processed by this type of exposure device, there is a trend toward using large-aperture, large-size semiconductor wafers, in the interests of increasing semiconductor element surface area and reducing costs. Further, there are needs for higher integration of semiconductor elements, high-speed and high-precision stage positioning, and higher through-put.
However, with conventional exposure devices, when increasing semiconductor wafer aperture size by moving the stage at high speed and with high precision, it is necessary to improve the motion characteristics of the stage. For this reason, it becomes necessary to improve guide rigidity, and the weight of the stage must be increased even more than the weight increase due to mere lengthening of the stroke. Moreover, aiming for higher through-put by attempting to increase stage motion acceleration and motion speed to reduce motion time causes further increase of excitation force due to stage motion acceleration. Consequently, the reaction force of driving the stage causes disturbance vibration to be transmitted to the exterior of the stage, which is likely to impair high-speed and high-precision positioning.
In view of these problems, stage devices provided with mass bodies, like that shown in FIG. 16, have been proposed.
In FIG. 16, 101 is an X stage for placement of a target object, and 102 is a Y stage which bears the X stage 101 and is movable in the Y direction with respect to a platform 103. On the Y stage 102 is provided an X-stage driving mechanism, made up of a ball screw 104 and a motor 105, which allows the X stage 101 to move in the X direction with respect to the Y stage 102. On the platform 103 is provided a Y-stage driving mechanism, made up of a ball screw 106 and a motor 107, which allows the Y stage to move in the Y direction with respect to the platform 103. By means of the foregoing structure, the X stage 101 can be positioned in the X and Y directions with respect to the platform 103. Further, on the platform 103 are provided mass bodies 108 through 111, which are movable in the X direction or the Y direction. The mass bodies are moved by ball screws 112 through 115 and motors 116 through 119, in order to cancel out reaction force and moment generated by motion of the stages.
With the foregoing structure, force generated in the platform by acceleration and deceleration of the stages is canceled out by motion of the mass bodies, thus absorbing vibration of the platform due to acceleration or deceleration of the stages.
In the foregoing structure, when the X stage is accelerated in a position offset from the center of gravity of the platform, in order to cancel out the moment arising in the platform, a mass body in a position symmetrical with that of the X stage with respect to the center of gravity of the platform is driven with acceleration in the same direction, relative to the other mass body, as the direction in which the center of gravity of the X stage is moving.
However, if, as shown in FIG. 7, the X stage continues a motion whereby it revolves around the center of gravity of the platform, positioning offset of the mass bodies accumulates, thus necessitating a stroke for driving the mass bodies. Further, regardless of how long the stroke of a mass body is made, if the moment arising in the platform is in the same direction, the position of the mass body will reach the end of its stroke.
The present invention has been made to solve the foregoing problems, and it is an object hereof to reduce reaction force, etc., caused by motion of a stage, while reducing the stroke lengths of mass bodies.
It is another object of the present invention to enable vibration caused by moving a mass body using a position compensation control system to be eliminated by an anti-vibration mechanism, and to enable reduction of mass body positioning offset without impairing performance of a positioning device.
It is a further object of the present invention to reduce the influence caused by moving a mass body using a position compensation control system to less than the precision required of a positioning device, and to maintain positioning precision while reducing the stroke lengths of mass bodies.
It is a further object of the present invention to enable the influence of a reaction force accompanying motion of a stage to be suppressed to less than the precision required of a positioning device, by moving mass bodies.
It is a further object of the present invention to shorten motion strokes of bass bodies while reducing reaction force in a parallel direction or in a rotational direction, caused by motion of stage. In particular, it is an object of the present invention to enable reduction of a reaction force in a rotational direction within the limited motion stroke of mass bodies.
It is a further object of the present invention to maintain highly precise positioning during exposure, when high precision is called for, by not performing compensation of mass body positioning offset.
Other features and advantages of the present invention will be apparent from the following description with reference to the accompanying drawings, in which like reference symbols designate the same or similar parts throughout the figures thereof.